Does Diatomaceous Earth Kill Black Widows?

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Updated on February 27, 2023

It might be true that black widow spiders aren’t as deadly as their reputations claim, but that’s not to say you want to risk getting bit by one. In fact, you won’t have much difficulty knowing what bit you when a black widow strikes. Even though they tend to be shy, it’s important to get rid of black widows before you have a nasty run-in.

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One popular remedy against insects is diatomaceous earth, which is safe to use around the house and can be quite effective. But will this remedy work against black widows? And if so, how effective is it, really? Let’s take a look at these questions and more.

Does Diatomaceous Earth Kill Black Widow Spiders?

Simply put, diatomaceous earth can kill black widows and a whole host of other creepy crawlies. However, how effective it is can depend on where and how it’s used.

So read on to learn everything you’ll need to know to make this amazing natural product work at peak efficiency.

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What is Diatomaceous Earth?

diatomaceous earth microscope

Diatomaceous earth (or DE for short) looks like a fine powder or sand, but there’s a lot more to it than meets the eye. It all begins with diatoms, a microscopic, single-celled type of algae with a hard shell that’s responsible for as much as 50 percent of the planet’s oxygen production.

There’s a wide variation in the shapes and sizes a diatom might have, and they’re believed to make up nearly half of the organic material in our oceans.

When diatoms die, their shells sink to the ocean floor and can be found as deep as a half mile below the bed’s surface. These shells can be harvested and are used in a wide range of products from toothpaste to rubber, dynamite, and even cat litter. But food-grade DE is perhaps best known for its use as a natural pesticide.

How Diatomaceous Earth Works

Because DE is made from crushed microscopic shells, it might be difficult to understand how it can kill. The real trick is size.

For humans and pets, DE is a powder or sand and might cause a bit of irritation to small paws, but is otherwise harmless. But shrink yourself to the size of a bug, and suddenly a bit of spilled DE looks like a minefield of broken glass.

The edges are so sharp, that they’ll lacerate any part of a bug that touches it. This scrapes away the waxy coating that keeps moisture in and protects the critter’s body and exoskeleton. Just like a deep cut across the skin, the bug will begin leaking bodily fluids until it ends up dying of dehydration.

While diatomaceous earth isn’t an instant killer, it has a high success rate due to the way it cuts those bugs unfortunate enough to crawl over it.

How to Use Diatomaceous Earth for Black Widows

The key to diatomaceous earth is getting a bug to actually come into contact with it. Thankfully, there are ways to make this happen even with spiders that aren’t likely to run around on a horizontal surface. The trick? Simply treat it as a powder.

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Look for spots where back widows or their prey are hiding and sprinkle a layer of DE on any surfaces in that area. You can place some DE on a paper towel and use your breath to gently blow it into spider webs and textured surfaces as well.

When the spider crosses over any of these surfaces, it can come into contact with the DE, which will lacerate its legs and any parts of the body that come into contact.

Note that DE is porous, so it becomes useless when it gets wet. Since it’s also a fine powder, you will need to add a fresh application every three days or so as well as after it’s exposed to rain or other forms of moisture.

See Also: 9 Most Common Spiders Found in Homes

How Long Does It Take To Work (and How Effective Is It)?

There are two common complaints regarding non-chemical pesticides that are often used to claim they don’t work.

  • The first is that they don’t kill instantly, meaning there’s a good chance you won’t see the corpses anywhere near the treated area.
  • The second is a problem that also affects non-residue chemical options, namely the fact that it only works when the pest comes into contact with the treatment.

Because of the way diatomaceous earth actually kills, it can take anywhere from a few hours to a few days for a victim to die after coming into contact with it. Spider eggs are least likely to be affected for the simple fact that they don’t move and therefore can only be damaged if something moves them while they’re in contact with DE.

Spiderlings are perhaps the quickest, since they have soft, small bodies that are closer to the ground and more easily damaged. However, an adult black widow is big enough that it might take a day or two to die.

Will DE Keep Black Widows Away?

black widow

Unfortunately, there’s a common misconception that the same product that kills a pest will also keep it from coming back. However, this is rarely the case.

Black widows will enter your home or property in search of food. If you want to prevent them from returning, you will need to locate and seal all potential entry points, as well as eliminating any pest populations that could provide food for the spiders.

There is one way in which DE does help keep spiders away, however. If you keep it sprinkled around your property in places spiders are likely to hunt, it will kill off their food supply, which gives black widows less reason to invade.

Just be warned that using diatomaceous earth outdoors can also kill beneficial critters that come into contact with it, since fossilized shell fragments aren’t very intelligent and won’t know the difference.

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So What DOES Help Keep Black Widows Away?

As mentioned, one of the best ways to keep black widows away is to clean house. This is a multi-step process meant to get rid of their food so they no longer have a reason to visit. Some important steps include:

  1. Seal any entry points so that black widows and their prey can’t get into your home. This includes making sure window screens aren’t damaged and any holes in outside walls are caulked or otherwise filled.
  2. Check regularly for any leaks in our home, such as a damaged pipe or water getting into the basement after a big storm and fix the problem. The moisture draws all sorts of pests in like a magnet, and black widows (or other predators) are sure to follow.
  3. Vacuum regularly. This not only removes food debris that can attract pests, but can also remove the pests themselves.  Again, this can go a long way towards keeping black widows from making a home in your home.
  4. Finally, you can use diatomaceous earth and similar products as a preventative. Sprinkle it around the foundation of your home to keep spiders and other critters from reaching the house. It can also be sprinkled along the bottom of doors or window sills to kill anything that gets in when these are opened.
Morgan

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